Environmentally-friendly vehicles, particularly electrically-powered vehicles such as electric vehicle and hybrid vehicle have recently been of interest. The electric vehicle is mounted with a power storage device, an inverter, and an electric motor driven by the inverter that serve as sources of motive power for the vehicle to travel. The hybrid vehicle is mounted with a power storage device, an inverter, and an electric motor in addition to an internal combustion engine that serve as sources of motive power for the vehicle to travel.
Regarding such electrically-powered vehicles, Japanese Patent Laying-Open No. 2005-51850 (PTD 1) discloses that, in response to detection of skid of a drive wheel driven by an electric motor, the electric motor is controlled so that the torque to be output to the drive shaft is restricted (see PTD 1).
As for control of an electric motor, PWM control is well known under which a pulse-width-modulated (PWM) voltage is applied to the electric motor. Control is also known under which the voltage utilization factor can be increased to a greater extent than the PWM control, specifically rectangular-wave voltage control is known under which a rectangular-wave voltage which is phase-controlled in accordance with a torque command (torque's target value) is applied to the electric motor.
Japanese Patent Laying-Open No. 2000-50689 (PTD 2) discloses, regarding the rectangular-wave voltage control of an electric motor, that the voltage phase of the rectangular-wave voltage is controlled based on a deviation of a detected value of the torque of the electric motor from a torque command value (see PTD 2)